Light-sensitive material containing silver halide, reducing agent and polymerizable compound wherein the silver halide is monodispersed

ABSTRACT

A light-sensitive material comprising a light-sensitive layer which contains silver halide grains, a reducing agent and a polymerizable compound provided on a support, characterized in that the silver halide grains have such a grain size distribution that the coefficient of variation (σ/r) is not more than 20% wherein σ means a standard deviation of the grain size and r means an average grain size. Image-forming methods employing the light-sensitive material are also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a light-sensitive material comprising alight-sensitive layer containing silver halide, a reducing agent and apolymerizable compound provided on a support, and further relates toimage-forming methods employing the light-sensitive material.

2. Description of Prior Arts

Light-sensitive materials comprising a light-sensitive layer containingsilver halide, a reducing agent and a polymerizable compound provided ona support can be used in an image forming method in which a latent imageof silver halide is formed, and then the polymerizable compound ispolymerized to form the corresponding image.

Examples of said image forming methods are described in Japanese PatentPublication Nos. 45(1970)-11149 (corresponding to U.S. Pat. No.3,697,275) 47(1972)-20741 (corresponding to U.S. Pat. No. 3,687,667) and49(1974)-10697, and Japanese Patent Provisional Publication Nos.57(1982)-138632, 57(1982)-142638, 57(1982)-176033, 57(1982)-211146(corresponding to U.S. Pat. No. 4,557,997), 58(1983)-107529(corresponding to U.S. Pat. No. 4,560,637), 58(1983)-121031(corresponding to U.S. Pat. No. 4,547,450) and 58(1983)-169143. In theseimage forming methods, when the exposed silver halide is developed usinga developing solution, the polymerizable compound is induced topolymerize in the presence of a reducing agent (which is oxidized) toform a polymer image. Thus, these methods need a wet development processemploying a developing solution. Therefore, the process takes arelatively long time.

An improved image forming method employing a dry process is described inJapanese Patent Provisional Publication Nos. 61(1986)-69062 and61(1986)-73145 (the contents of both publications are described in U.S.Pat. No. 4,629,676 and European Patent Provisional Publication No.0174634A2). In this image forming method, a recording material (i.e.,light-sensitive material) comprising a light-sensitive layer containinga light-sensitive silver salt (i.e., silver halide), a reducing agent, across-linkable compound (i.e., polymerizable compound) and a binderprovided on a support is imagewise exposed to form a latent image, andthen the material is heated to polymerize within the area where thelatent image of the silver halide has been formed. The above methodemploying the dry process and the light-sensitive material employablefor such method are also described in Japanese Patent ProvisionalPublication Nos. 61(1986)-183640, 61(1986)-188535 and 61(1986)-228441.

The above-mentioned image forming methods are based on the principle inwhich the polymerizable compound is polymerized within the area where alatent image of the silver halide has been formed.

Further, Japanese Patent Provisional Publication No. 61(1986)-260241describes another image forming method in which the polymerizablecompound in a portion where a latent image of the silver halide has notbeen formed is polymerized. In this method, when the material is heated,the reducing agent functions as polymerization inhibitor within the areawhere a latent image of the silver halide has been formed, and thepolymerizable compound in the other portion is polymerized.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a light-sensitivematerial which gives an image reduced in occurrence of fog.

Another object of the invention is to provide a light-sensitive materialwhich gives a clear image, even if small amount of the silver halide isused.

There is provided by the present invention a light-sensitive materialcomprising a light-sensitive layer which contains silver halide grains,a reducing agent and a polymerizable compound provided on a support,characterized in that the silver halide grains have such a grain sizedistribution that the coefficient of variation (in terms of σ/r) is notmore than 20%, wherein σ means a standard deviation of the grain sizeand r means an average grain size.

The light-sensitive material of the invention can be advantageously usedin a process which comprises:

imagewise exposing the light-sensitive material to form a latent imageof the silver halide, and

heating the light-sensitive material either simultaneously with or afterthe imagewise exposure to polymerize the polymerizable compound withinthe area where the latent image of the silver halide has been formed (orthe area where the latent image of the silver halide has not beenformed).

The light-sensitive material of the invention is characterized in thatthe silver halide grains have a narrow grain size distribution in whichthe coefficient of the variation in terms of σ/r is not more than 20%.

The present inventor has found that the light-sensitive materialemploying said silver halide grains is reduced in the occurrence of fogand accelerated in the development. Therefore, the light-sensitivematerial of the invention can form an improved clear image having a highmaximum density and a low minimum density.

In the light-sensitive material of the invention, the silver halidegrain functions as a photo-sensor, and the grain is imagewise developedto accelerate or inhibit the following polymerization. If the silverhalide grains have an excessively broad grain size distribution, a partof the grains can not be smoothly developed in the development process,and thereby the ratio of the grains participating in the developmentbecomes small. Therefore, the silver halide grains having the abovenarrow grain size distribution can effectively form a polymerizationimage, even if small amount of the silver halide is used. The aboveeffect in the light-sensitive material of the invention is surprisinglyremarkable beyond the knowledge in the conventional photographic system.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, there is no specific limitation with respectto the halogen composition of the silver halide grain. Examples of thesilver halide include silver chloride, silver bromide, silver iodide,silver chlorobromide, silver chloroiodide, silver iodobromide and silverchloroiodobromide in the form of the grains. The halogen composition ofindividual grains may be homogeneous or heterogeneous.

In the light-sensitive material of the invention, the silver halidegrains have a narrow grain size distribution in which the coefficient ofvariation in terms of σ/r is not more than 20%, wherein σ is thestandard deviation of the grain size and r is the average grain size.

The grain size (r) of the silver halide grain can be calculatedaccording to the following formula (I), in which S means the area of theprojected image of the silver halide grain. ##EQU1##

Further, the average grain size (r) of the silver halide grains can becaluculated according to the following formula (II), in which ri is theindividual grain size caluculated according to the above formula (I) andn is the number of the caluculated silver halide grains contained in thelight-sensitive layer. ##EQU2##

Furthermore, the standard deviation of the grain size (σ) is defined bythe following formula (III). ##EQU3##

The coefficient of variation (σ/r) in the grain size distribution can beobtained from the average grain size (r) and the standard deviation (σ).In the present invention, the coefficient of variation is not more than20% (0.20), and more preferably not more than 15% (0.15).

Examples of a conventional photographic light-sensitive material and asilver halide emulsion employing the silver halide grains which have thenarrow grain size distribution are described in Japanese PatentProvisional Publication Nos. 57(1982)-178235, 58(1983)-100846 and58(1983)-14829, International Patent Publication No. 83-02330A1, andEuropean Patent Provisional Publication Nos. 64412A3 and 83377A1.

The silver halide grains ordinarily have an average grain size (r) inthe range of 0.001 to 5 μm, more preferably 0.001 to 2 μm.

In the case that the silver halide grains are contained in amicrocapusle, the average grain size of silver halide grains preferablyis not more than one-fifth of the average size of the microcapsules,more preferably is not more than the one-tenth.

When the grain size of the silver halide becomes larger beyond a certainlevel, only a small number of the silver halide grains can beincorporated into a microcapsule. Therefore, the numbers of the silverhalide grains incorporated into respective individual microcapusleslargely varies from each other. As a result, even if the microcapsulesare irradiated with same quantity of radiation, it may happen thatpolymerization occurs in certain microcapsules, while polymerizationdoes not appropriately occur in neighboring other microcapsules.Therefore, excessive variation of the number of silver halide grainsamong microcapusles is supposed to bring about uneveness (roughness)into the obtained image. It is observed that when the average size ofthe microcapsules is not less than 5 times as much as the average grainsize of silver halide grains, even and uniform image can be obtained.

There is no specific limitation on the crystal habit of the silverhalide grain. Two or more kinds of silver halide grains which differ incrystal habit, grain size, and/or other features from each other can beused in combination, so long as the silver halide grains have theabove-mentioned grain size distribution.

The total silver content (including silver halide and an organic silversalt which is one of optional components) in the light-sensitive layerpreferably is in the range of from 0.1 mg/m² to 10 g/m². The silvercontent of the silver halide in the light-sensitive layer preferably isnot more than 1 g/m², more preferably in the range of from 1 mg to 500mg/m².

The silver halide grains can be prepared, for instance by the followingprocess.

The silver halide grain is preferably prepared in the form of a silverhalide emulsion. Various processes for the preparation of the silverhalide emulsion are known in the conventional technology for thepreparation of photographic materials.

The silver halide grains having the above-mentioned grain sizedistribution can be prepared by adjusting the conditions in the grainformation, such as pH, pAg, temperature, the form and the scale of thereaction vessel and the reaction method. There is no specific limitationwith respect to the grain formation of the silver halide grains for thepreparation of the light-sensitive material of the invention.

Preparation of a silver halide emulsion containing the silver halidegrains which have the narrow grain size distribution is described inJapanese Patent Provisional Publication Nos. 57(1982)-178235,58(1983)-100846 and 58(1983)-14829, International Patent Publication No.83-02330A1, and European Patent Provisional Publication Nos. 64412A3 and83377A1.

The silver halide emulsion can be prepared by the acid process, neutralprocess or ammonia process. In the stage for the preparation, a solublesilver salt and a halogen salt can be reacted in accordance with thesingle jet process, double jet process or a combination thereof. Areverse mixing method, in which grains are formed in the presence ofexcess silver ions, or a controlled double jet process, in which a pAgvalue is maintained constant, can be also employed. In order toaccelerate grain growth, the concentrations or amounts or the silversalt and halogen salt to be added or the rate of their addition can beincreased as described in Japanese Patent Provisional Publication Nos.55(1980)-142329 and 55(1980)-158124, and U.S. Pat. No. 3,650,757, etc.

The silver halide emulsion may be of a surface latent image type thatforms a latent image predominantly on the surface of silver halidegrains, or of an inner latent image type that forms a latent imagepredominantly in the interior of the grains. A direct reversal emulsioncomprising an inner latent image type emulsion and a nucleating agentmay be employed. The inner latent image type emulsion suitable for thispurpose is described in U.S. Pat. Nos. 2,592,250 and 3,761,276, JapanesePatent Publication No. 58(1983)-3534 and Japanese Patent ProvisionalPublication No. 57(1982)-136641, etc. The nucleating agent that ispreferably used in combination with the inner latent image type emulsionis described in U.S. Pat. Nos. 3,227,552, 4,245,037, 4,255,511,4,266,013 and 4,276,364, and West German Patent Provisional Publication(OLS) No. 2,635,316.

In the preparation of the silver halide emulsions, hydrophilic colloidsare advantageously used as protective colloids. Examples of usablehydrophilic colloids include proteins, e.g., gelatin, gelatinderivatives, gelatin grafted with other polymers, albumin, and casein;cellulose derivatives, e.g., hydroxyethyl cellulose, carboxymethylcellulose, cellulose sulfate, etc.; saccharide derivatives, e.g., sodiumalginate and starch derivatives; and a wide variety of synthetichydrophilic polymers, such as polyvinyl alcohol, polyvinyl alcoholpartial acetal, poly-N-vinylpyrrolidone, polyacrylic acid,polymethacrylic acid, polyacrylamide, polyvinylimidazole, andpolyvinylpyrazole, and copolymers comprising monomers constituting thesehomopolymers. Among them, gelatin is most preferred. Examples ofemployable gelatins include not only lime-processed gelatin, but alsoacid-processed gelatin and enzyme-processed gelatin. Hydrolysis productsor enzymatic decomposition products of gelatin can also be used.

In the formation of silver halide grains in the silver halide emulsion,ammonia, an organic thioether derivative as described in Japanese PatentPublication No. 47(1972)-11386 or sulfur-containing compound asdescribed in Japanese Patent Provisional Publication No. 53(1978)-144319can be used as a silver halide solvent. Further, in the grain formationor physical ripening, a cadmium salt, a zinc salt, a lead salt, athallium salt, or the like can be introduced into the reaction system.Furthermore, for the purpose of improving high or low intensityreciprocity law failure, a water-soluble iridium salt, e.g., iridium(III) or (IV) chloride, or ammonium hexachloroiridate, or awater-soluble rhodium salt, e.g., rhodium chloride can be used.

After the grain formation or physical ripening, soluble salts may beremoved from the resulting emulsion by a known noodle washing method ora sedimentation method. The silver halide emulsion may be used in theprimitive condition, but is usually subjected to chemical sensitization.Chemical sensitization can be carried out by the sulfur sensitization,reduction sensitization or noble metal sensitization, or a combinationthereof that are known for emulsions for the preparation of theconventional light-sensitive materials.

When the sensitizing dyes are added to the silver halide emulsion, thesensitizing dye is preferably added during the preparation of theemulsion.

The reducing agent, the polymerizable compound and the support whichconstitute the light-sensitive material of the invention with the silverhalide grains are stated below. Thus composed material is referredhereinafter to as the "light-sensitive material".

The reducing agent employed in the light-sensitive material has afunction of reducing the silver halide and/or a function of acceleratingor restraining polymerization of the polymerizable compound. Examples ofthe reducing agents having these functions include various compounds,such as hydroquinones, catechols, p-aminophenols, p-phenylenediamines,3-pyrazolidones, 3-aminopyrazoles, 4-amino-5-pyrazolones,5-aminouracils, 4,5-dihydroxy-6-aminopyrimidines, reductones,aminoreductones, o- or p-sulfonamidophenols, o- orp-sulfonamidonaphthols, 2-sulfonamidoindanones,4-sulfonamido-5-pyrazolones, 3-sulfonamidoindoles,sulfonamidopyrazolobenzimidazoles, sulfonamidopyrazolotriazoles,α-sulfonamidoketones, hydrazines, etc. Depending on the nature or amountof the reducing agent, the polymerizable compound in either a portionwhere a latent image of the silver halide has been formed or a portionwhere a latent image of the silver halide has not been formed can bepolymerized. In the developing system in which the polymerizablecompound in the portion where the latent image has not been formed ispolymerized, 1-phenyl-3-pyrazolidone is preferably employed as thereducing agent.

The light-sensitive materials employing the reducing agent having thesefunctions (including compounds referred to as developing agent orhydrazine derivative) are described in Japanese Patent ProvisionalPublication Nos. 61(1986)-183640, 61(1986)-188535 and 61(1986)-228441,and Japanese Patent Application Nos. 60(1985)-210657, 60(1985)-226084,60(1985)-227527 and 60(1985)-227528. These reducing agents are alsodescribed in T. James, "The Theory of the Photographic Process", 4thedition, 291-334 (1977), Research Disclosure No. 17029, 9-15 (June1978), and Research Disclosure No. 17643, 22-31 (Dec. 1978). Thereducing agents described in the these publications and applications canbe employed in the light-sensitive material of the present invention.Thus, "the reducing agent(s)" in the present specification means toinclude all of the reducing agents described in the above mentionedpublications and applications.

These reducing agents can be used singly or in combination. In the casethat two or more reducing agents are used in combination, certaininteractions between these reducing agents may be expected. One of theinteractions is for acceleration of reduction of silver halide (and/oran organic silver salt) through so-called superadditivity. Anotherinteraction is for a chain reaction in which an oxidized state of onereducing agent formed by a reduction of silver halide (and/or an organicsilver salt) induces or inhibits the polymerization of the polymerizablecompound via oxidation-reduction reaction with another reducing agent.Both interactions may occur simultaneously. Thus, it is difficult todetermine which of the interactions has occurred in practical use.

Examples of these reducing agents include pentadecylhydroquinone,5-t-butylcatechol, p-(N,N-diethylamino)phenol,1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone,1-phenyl-4-methyl-4-heptadecylcarbonyloxymethyl-3-pyrazolidone,2-phenylsulfonylamino-4-hexadecyloxy-5-t-octylphenol,2-phenylsulfonylamino-4-t-butyl-5-hexadecyloxyphenol,2-(N-butylcarbamoyl)-4-phenylsulfonylaminonaphtol,2-(N-methyl-N-octadecylcarbamoyl)-4-sulfonylaminonaphthol,1-acetyl-2-phenylhydrazine, 1-acetyl-2-(p- or o-aminophenyl)hydrazine,1-formyl-2-(p- or o-aminophenyl)hydrazine, 1-acetyl-2-(p- oro-methoxyphenyl)hydrazine, 1-lauroyl-2-(p- or o-aminophenyl)hydrazine,1-trityl-2-(2,6-dichloro-4-cyanophenyl)hydrazine,1-trityl-2-phenylhydrazine, 1-phenyl-2-(2,4,6-trichlorophenyl)hydrazine,1-{2-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p- oro-aminophenyl)hydrazine, 1-{2-(2,5-di-t-pentylphenoxy)butyloyl}-2-(p-oro-aminophenyl)hydrazine pentadecylfluorocaprylate salt, 3-indazolinone,1-(3,5-dichlorobenzoyl)-2-phenylhydrazine,1-trityl-2-[{(2-N-butyl-N-octylsulfamoyl)-4-methanesulfonyl}phenyl]hydrazine,1-{4-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p- oro-methoxyphenyl)hydrazine,1-(methoxycarbonylbenzohydryl)-2-phenylhydrazine,1-formyl-2-[4-{2-(2,4-di-tert-pentylphenoxy)butylamide}phenyl]hydrazine,1-acetyl-2-[4-{2-(2,4-di-tert-pentylphenoxy)butylamido}phenyl]hydrazine,1-trityl-2-[{2,6-dichloro-4-(N,N-di-2-ethylhexyl)carbamoyl}phenyl]hydrazine,1-(methoxycarbonylbenzohydryl)-2-(2,4-dichlorophenyl)hydrazine and1-trityl-2-[{2-(N-ethyl-N-octylsulfamoyl)-4-methanesulfonyl}phenyl]hydrazine.

The amount of the reducing agent in the light-sensitive layer preferablyranges from 0.1 to 1,500 mole % based on the amount of silver (containedin the abovementioned silver halide and an organic silver salt).

There is no specific limitation with respect to the polymerizablecompound, and any known polymerizable compounds including monomers,oligomers and polymers can be contained in the light-sensitive layer. Inthe case that heat development (i.e., thermal development) is utilizedfor developing the light-sensitive material, the polymerizable compoundshaving a relatively higher boiling point (e.g., 80° C. or higher) thatare hardly evaporated upon heating are preferably employed. In the casethat the light-sensitive layer contains a color image forming substance,the polymerizable compounds are preferably cross-linkable compoundshaving plural polymerizable groups in the molecule, because suchcross-linkable compounds favorably serve for fixing the color imageforming substance in the course of polymerization hardening of thepolymerizable compounds.

The polymerizable compound employable for the light-sensitive materialof the invention are described in the above-mentioned andlater-mentioned publications and applications concerning thelight-sensitive material.

Preferred polymerizable compounds employable for the light-sensitivematerial are compounds which are polymerizable through addition reactionor ring-opening reaction. Preferred examples of the compounds beingpolymerizable through addition reaction include compounds having anethylenic unsaturated group. Preferred examples of the compounds beingpolymerizable through ring-opening reaction include the compounds havingan epoxy group. Among them, the compounds having an ethylenicunsaturated group are preferred.

Examples of compounds having an ethylenic unsaturated group includeacrylic acid, salts of acrylic acid, acrylic esters, acrylamides,methacrylic acid, salts of methacrylic acid, methacrylic esters,methacrylamide, maleic anhydride, maleic esters, itaconic esters,styrene, styrene derivatives, vinyl ethers, vinyl esters, N-vinylheterocyclic compounds, allyl ethers, allyl esters, and compoundscarrying a group or groups corresponding to one or more of thesecompounds.

Concrete examples of the acrylic esters include n-butyl acrylate,cyclohexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, furfurylacrylate, ethoxyethoxy acrylate, dicyclohexyloxyethyl acrylate,nonylphenyloxyethyl acrylate, hexanediol diacrylate, butanedioldiacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate,pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,diacrylate of polyoxyethylenated bisphenol A, polyacrylate ofhydroxypolyether, polyester acrylate, and polyurethane acrylate.

Concrete examples of the methacrylic esters include methyl methacrylate,butyl methacrylate, ethylene glycol dimethacrylate, butanedioldimethacrylate, neopentylglycol dimethacrylate, trimethylolpropanetrimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, and dimethacrylate of polyoxyalkylenated bisphenol A.

The polymerizable compounds can be used singly or in combination of twoor more compounds. Further, compounds formed by bonding a polymerizablegroup such as a vinyl group or a vinylidene group to a reducing agent ora color image forming substance are also employed as the polymerizablecompounds. The light-sensitive materials employing these compounds whichshow functions as both the reducing agent and the polymerizablecompound, or of the color image forming substance and the polymerizablecompound, are included in embodiments of the invention.

The amount of the polymerizable compound for incorporation into thelight-sensitive layer preferably ranges from 5 to 1.2×10⁵ times (byweight) as much as the amount of silver halide, more preferably from 10to 1×10⁴ times as much as the silver halide.

The light-sensitive material of the invention can be prepared byarranging a light-sensitive layer containing the above-mentionedcomponents on a support. There is no limitation with respect to thesupport. In the case that heat development is utilized in the use of thelight-sensitive material, the material of the support preferably isresistant to heat given in the processing stage. Examples of thematerial employable for the preparation of the support include glass,paper, fine paper, coat paper, synthetic paper, metals and analoguesthereof, polyester, acetyl cellulose, cellulose ester, polyvinyl acetal,polystyrene, polycarbonate, polyethylene terephthalate, and paperlaminated with resin or polymer (e.g., polyethylene).

Various embodiments of the light-sensitive materials, optionalcomponents which may be contained in the light-sensitive layer, andauxiliary layers which may be optionally arranged on the light-sensitivematerials are described below.

The polymerizable compound is preferably dispersed in the form of oildroplets in the light-sensitive layer. Other components in thelight-sensitive layer, such as silver halide, the reducing agent, thecolor image forming substances may be also contained in the oildroplets.

The oil droplets of the polymerizable compound are preferably preparedin the form of microcapsules. There is no specific limitation onpreparation of the microcapsules. There is also no specific limitationon shell material of the microcapsule, and various known materials suchas polymers which are employed in the conventional microcapsules can beemployed as the shell material. The mean size of the microcapsulepreferably ranges from 0.5 to 50 μm, more preferably 1 to 25 μm, mostpreferably 3 to 20 μm.

The light-sensitive layer can further contain optional components suchas color image forming substances, sensitizing dyes, organic silversalts, various kinds of image formation accelerators, thermalpolymerization inhibitors, thermal polymerization initiators,development stopping agents, fluorescent brightening agents,discoloration inhibitors, antihalation dyes or pigments, antiirradiationdyes or pigments, matting agents, antismudging agents, plasticizers,water releasers and binders.

There is no specific limitation with respect to the color image formingsubstance, and various kinds of substances can be employed. Thus,examples of the color image forming substance include both coloredsubstance (i.e., dyes and pigments) and non-colored or almostnon-colored substance (i.e., color former or dye- or pigment-precursor)which develops to give a color under application of external energy(e.g., heating, pressing, light irradiation, etc.) or by contact withother components (i.e., developer). The light-sensitive material usingthe color image forming substance is described in Japanese PatentProvisional Publication No. 61(1986)-73145.

Examples of the dyes and pigments (i.e., colored substances) employablein the invention include commercially available ones, as well as variousknown compounds described in the technical publications, e.g., YukiGosei Kagaku Kyokai (ed.), Handbook of Dyes (in Japanese, 1970) andNippon Ganryo Gijutsu Kyokai (ed.), New Handbook of Pigments (inJapanese, 1977). These dyes and pigments can be used in the form of asolution or a dispersion.

Examples of the substances which develop to give a color by certainenergy includes thermochromic compounds, piezochromic compounds,photochromic compounds and leuco compounds derived from triarylmethanedyes, quinone dyes, indigoid dyes, azine dyes, etc. These compounds arecapable of developing a color by heating, application of pressure,light-irradiation or air-oxidation.

Examples of the substances which develop to give a color in contact withother components include various compounds capable of developing a colorthrough some reaction between two or more components, such as acid-basereaction, oxidation-reduction reaction, coupling reaction, chelatingreaction, and the like. Examples of such color formation systems aredescribed in Hiroyuki Moriga, "Introduction of Chemistry of SpecialityPaper" (in Japanese, 1975), 29-58 (pressure-sensitive copying paper),87-95 (azo-graphy), 118-120 (heat-sensitive color formation by achemical change) or in MSS. of the seminer promoted by the Society ofKinki Chemical Industry, "The Newest Chemistry of Coloring Matter -Attractive Application and New Development as a Functional ColoringMatter", 26-32 (June, 19, 1980). Examples of the color formation systemsspecifically include a color formation system used in pressure-sensitivepapers, etc., comprising a color former having a partial structure oflactone, lactam, spiropyran, etc., and an acidic substance (developer),e.g., acid clay, phenol, etc.; a system utilizing azo-coupling reactionbetween an aromatic a diazonium salt, diazotate or diazosulfonate andnaphthol, aniline, active methylene, etc.; a system utilizing achelating reaction, such as a reaction between hexamethylenetetramineand a ferric ion and gallic acid, or a reaction between aphenolphthalein-complexon and an alkaline earth metal ion; a systemutilizing oxidation-reduction reaction, such as a reaction betweenferric stearate and pyrogallol, or a reaction between silver behenateand 4-methoxy-1-naphthol, etc.

The color image forming substance in the light-sensitive material ispreferably used in an amount of from 0.5 to 50 parts by weight, and morepreferably from 2 to 30 parts by weight, per 100 parts by weight of thepolymerizable compound. In the case that the developer is used, it ispreferably used in an amount of from about 0.3 to about 80 parts byweight per one part by weight of the color former.

There is no specific limitation with respect to the sensitizing dyes,and known sensitizing dyes used in the conventional art of photographymay be employed in the light-sensitive material of the invention.Examples of the sensitizing dyes include methine dyes, cyanine dyes,merocyanine dyes, complex cyanine dyes, complex merocyanine dyes,holopolar cyanine dyes, hemicyanine dyes, styryl dyes, and hemioxonoldyes. These sensitizing dyes can be used singly or in combination.Combinations of sensitizing dyes are often used for the purpose ofsupersensitization. In addition to the sensitizing dyes, a substancewhich does not per se exhibit spectral sensitization effect or does notsubstantially absorb visible light but shows supersensitizing activitycan be used. The amount of the sensitizing dye to be added generallyranges from about 10⁻⁸ to about 10⁻² mol per 1 mol of silver halide. Thesensitizing dye is preferably added during the stage of the preparationof the silver halide emulsion.

When the heat development is employed in the use of the light-sensitivematerial, an organic silver salt is preferably contained in thelight-sensitive material. It can be assumed that the organic silver salttakes part in a redox reaction using a silver halide latent image as acatalyst when heated to a temperature of 80° C. or higher. In such case,the silver halide and the organic silver salt preferably are located incontact with each other or close together. Examples of organic compoundsemployable for forming such organic silver salt include aliphatic oraromatic carboxylic acids, thiocarbonyl group-containing compoundshaving a mercapto group or an α-hydrogen atom, imino group-containingcompounds, and the like. Among them, benzotriazoles are most preferable.The organic silver salt is preferably used in an amount of from 0.01 to10 mol., and preferably from 0.01 to 1 mol., per 1 mol. of thelight-sensitive silver halide. Instead of the organic silver salt, anorganic compound (e.g., benzotriazole) which can form an organic silversalt in combination with an inorganic silver salt can be added to thelight-sensitive layer to obtain the same effect.

Various image formation accelerators are employable in thelight-sensitive material of the invention. The image formationaccelerators have a function to accelerate the oxidation-reductionreaction between a silver halide (and/or an organic silver salt) and areducing agent, a function to accelerate emigration of an image formingsubstance from a light-sensitive layer to an image-receiving material oran image-receiving layer, or a similar function. The image formationaccelerators can be classified into inorganic bases, organic bases, baseprecursors, oils, surface active agents, hot-melt solvents, and thelike. These groups, however, generally have certain combined functions,i.e., two or more of the above-mentioned effects. Thus, the aboveclassification is for the sake of convenience, and one compound oftenhas a plurality of functions combined.

Various examples of these image formation accelerators are shown below.

Preferred examples of the inorganic bases include hydroxides of alkalimetals or alkaline earth metals; secondary or tertiary phosphates,borates, carbonates, quinolinates and metaborates of alkali metals oralkaline earth metals; a combination of zinc hydroxide or zinc oxide anda chelating agent (e.g., sodium picolinate); ammonium hydroxide;hydroxides of quaternary alkylammoniums; and hydroxides of other metals.Preferred examples of the organic bases include aliphatic amines (e.g.,trialkylamines, hydroxylamines and aliphatic polyamines); aromaticamines (e.g., N-alkyl-substituted aromatic amines,N-hydroxylalkyl-substituted aromatic amines andbis[p-(dialkylamino)phenyl]-methanes), heterocyclic amines, amidines,cyclic amidines, guanidines, and cyclic guanidines. Of these bases,those having a pKa of 7 or more are preferred.

The base precursors preferably are those capable of releasing bases uponreaction by heating, such as salts between bases and organic acidscapable of decarboxylation by heating, compounds capable of releasingamines through intramolecular nucleophilic substitution, Lossenrearrangement, or Beckmann rearrangement, and the like; and thosecapable of releasing bases by electrolysis. Preferred examples of thebase precursors include guanidine trichloroacetate, piperidinetrichloroacetate, morpholine trichloroacetate, p-toluidinetrichloroacetate, 2-picoline trichloroacetate, guanidinephenylsulfonylacetate, guanidine 4-chlorophenylsulfonylacetate,guanidine 4-methyl-sulfonylphenylsulfonylacetate, and4-acetylaminomethyl propionate.

These bases or base precursors are preferably used in an amount of notmore than 100% by weight, and more preferably from 0.1 to 40% by weight,based on the total solid content of the light-sensitive layer. Thesebases or base precursors can be used singly or in combination.

Examples of the oils employable in the invention include high-boilingorganic solvents which are used as solvents in emulsifying anddispersing hydrophobic compounds.

Examples of the surface active agents employable in the inventioninclude pyridinium salts, ammonium salts and phosphonium salts asdescribed in Japanese Patent Provisional Publication No. 59(1984)-74547;polyalkylene oxides as described in Japanese Patent ProvisionalPublication No. 59(1984)-57231.

The hot-melt solvents preferably are compounds which may be used as asolvent of the reducing agent or those which have high dielectricconstant and can accelerate physical development of silver salts.Examples of the hot-melt solvents include polyethylene glycols,derivatives of polyethylene oxides (e.g., oleate ester), beeswax,,monostearin and high dielectric constant compounds having --SO₂ --and/or --CO-- group described in U.S. Pat. No. 3,347,675; polarcompounds described in U.S. Pat. No. 3,667,959; and 1,10-decanediol,methyl anisate and biphenyl suberate described in Research Disclosure26-28 (Dec. 1976). The hot-melt solvent is preferably used in an amountof from 0.5 to 50% by weight, and more preferably from 1 to 20% byweight, based on the total solid content of the light-sensitive layer.

The thermal polymerization initiators employable in the light-sensitivematerial preferably are compounds that are decomposed under heating togenerate a polymerization initiating species, particularly a radical,and those commonly employed as initiators of radical polymerization. Thethermal polymerization initiators are described in "AdditionPolymerization and Ring Opening Polymerization", 6-18, edited by theEditorial Committee of High Polymer Experimental Study of the HighPolymer Institute, published by Kyoritsu Shuppan (1983). Examples of thethermal polymerization initiators include azo compounds, e.g.,azobisisobutyronitrile, 1,1'-azobis(1-cyclohexanecarbonitrile), dimethyl2,2'-azobisisobutyrate, 2,2'-azobis(2-methylbutyronitrile), andazobisdimethylvaleronitrile; organic peroxides, e.g., benzoyl peroxide,di-tert-butyl peroxide, dicumyl peroxide, tertbutyl hydroperoxide, andcumene hydroperoxide; inorganic peroxides, e.g., hydrogen peroxide,potassium persulfate, and ammonium persulfate; and sodiump-toluenesulfinate. The thermal polymerization initiators are preferablyused in an amount of from 0.1 to 120% by weight, and more preferablyfrom 1 to 10% by weight, based on amount of the polymerizable compound.In a system in which the polymerizable compound located in a portionwhere the latent image has not been formed is polymerized, the thermalpolymerization initiators are preferably incorporated into thelight-sensitive layer. The light-sensitive material employing thethermal polymerization initiators is described in Japanese PatentProvisional Publication No. 61(1986)-260241.

The development stopping agents employable in the light-sensitivematerial are compounds that neutralize a base or react with a base toreduce the base concentration in the layer to thereby stop development,or compounds that mutually react with silver or a silver salt tosuppress development. More specifically, examples of the developmentstopping agents include acid precursors capable of releasing acids uponheating electrophilic compounds capable of undergoing substitutionreaction with a coexisting base upon heating, nitrogen-containingheterocyclic compounds, mercapto compounds, and the like. Examples ofthe acid precursors include oxide esters described in Japanese PatentProvisional Publication Nos. 60(1985)-108837 and 60(1985)-192939 andcompounds which release acids through Lossen rearrangement described inJapanese Patent Provisional Publication No. 60(1985)-230133. Examples ofthe electrophilic compounds which induce substitution reaction withbases upon heating are described in Japanese Patent ProvisionalPublication No. 60(1985)-230134.

The antismudging agents employable in the light-sensitive materialpreferably are particles which are solid at ambient temperatures.Examples of the antismudging agents include starch particles describedin U.K. Patent No. 1,232,347; polymer particles described in U.S. Pat.No. 3,625,736; microcapsule particles containing no color formerdescribed in U.K. Patent No. 1,235,991; and cellulose particles, andinorganic particles, such as particles of talc, kaolin, bentonite,agalmatolite, zinc oxide, titanium dioxide or aluminium oxide describedin U.S. Pat. No. 2,711,375. Such particles preferably have a mean sizeof 3 to 50 μm, more preferably 5 to 40 μm. When the microcapsule isemployed in the light-sensitive material, the size of said particle ispreferably larger than that of the microcapsule.

Binders employable in the light-sensitive material preferably aretransparent or semi-transparent hydrophilic binders. Examples of thebinders include natural substances, such as gelatin, gelatinderivatives, cellulose derivatives, starch, and gum arabic; andsynthetic polymeric substances, such as water-soluble polyvinylcompounds e.g., polyvinyl alcohol, polyvinylpyrrolidone, and acrylamidepolymers. In addition to the synthetic polymeric substances, vinylcompounds dispersed in the form of latex, which are particularlyeffective to increase dimensional stability of photographic materials,can be also used. These binders can be used singly or in combination.The light-sensitive material employing a binder is described in JapanesePatent Provisional Publication No. 61(1986)-69062.

Examples and usage of the other optional components which can becontained in the light-sensitive layer are also described in theabove-mentioned publications and applications concerning thelight-sensitive material, and in Research Disclosure Vol. 170, No.17029, 9-15 (June 1978).

Examples of auxiliary layers which are optionally arranged on thelight-sensitive material include an image-receiving layer, a heatinglayer, an antistatic layer, an anticurl layer and a release layer.

Instead of the use of the image-receiving material, the image-receivinglayer can be arranged on the light-sensitive material to produce thedesired image on the on the image-receiving layer of the light-sensitivematerial. The image-receiving layer of the light-sensitive material canbe constructed in the same manner as the layer of the image-receivingmaterial. The details of the image-receiving layer will be describedlater.

Examples and usage of the other auxiliary layers are also described inthe above-mentioned publications and applications concerning thelight-sensitive material.

The light-sensitive material of the invention can be prepared, forinstance, by the following process.

The light-sensitive material is usually prepared by dissolving,emulsifying or dispersing each of the components of the light-sensitivelayer in an adequate medium to obtain coating solution, and then coatingthe obtained coating solution on a support.

The coating solution can be prepared by mixing liquid compositions eachcontaining a component of the light-sensitive layer. Liquid compositioncontaining two or more components may be also used in the preparation ofthe coating solution. Some components of the light-sensitive layer canbe directly added to the coating solution or the liquid composition.Further, a secondary composition can be prepared by emulsifying the oily(or aqueous) composition in an aqueous (or oily) medium to obtain thecoating solution.

In preparation of the light-sensitive material, the polymerizablecompounds are used as the medium for preparation of the liquidcomposition containing another component of the light-sensitive layer.For example, the silver halide (including the silver halide emulsion),the reducing agent, or the color image forming substance can bedissolved, emulsified or dispersed in the polymerizable compound toprepare the light-sensitive material. Especially, the color imageforming substance is preferably incorporated into the polymerizablecompound. Further, the necessary components for the preparation ofmicrocapsules, such as shell material can be incorporated into thepolymerizable compound.

The light-sensitive composition which is the polymerizable compoundcontaining the silver halide can be prepared using the silver halideemulsion. The light-sensitive composition can be also prepared usingsilver halide powders which can be prepared by lyophilization. Thelight-sensitive composition can be obtained by stirring thepolymerizable compound and the silver halide using a homogenizer, ablender, a mixer or other conventional stirring device.

Polymers having a principal chain consisting essentially of ahydrocarbon chain substituted in part with hydrophilic groups whichcontain, in their terminal groups, --OH or nitrogen having a loneelectron-pair are preferably introduced into the polymerizable compoundprior to the preparation of the light-sensitive composition. The polymerhas a function of dispersing silver halide or other component in thepolymerizable compound very uniformly as well as a function of keepingthus dispersed state. Further, the polymer has another function ofgathering silver halide along the interface between the polymerizablecompound (i.e., light-sensitive composition) and the aqueous medium inpreparation of the microcapsule. Therefore, using this polymer, silverhalide can be easily introduced into the shell material of themicrocapsule.

The polymerizable compound (including the light-sensitive composition)is preferably emulsified in an aqueous medium to prepare the coatingsolution. The necessary components for preparation of the microcapsule,such as shell material can be incorporated into the emulsion. Further,other components such as the reducing agent can be added to theemulsion.

The emulsion of the polymerizable compound can be processed for formingthe shell of the microcapsule. Examples of the process for thepreparation of the microcapsules include a process utilizingcoacervation of hydrophilic wall-forming materials as described in U.S.Pat. Nos. 2,800,457 and 2,800,458; an interfacial polymerization processas described in U.S. Pat. No. 3,287,154, U.K. Pat. No. 990,443 andJapanese Patent Publication Nos. 38(1963)-19574, 42(1967)-466 and42(1967)-771; a process utilizing precipitation of polymers as describedin U.S. Pat. Nos. 3,418,250 and 3,660,304; a process of usingisocyanate-polyol wall materials as described in U.S. Pat. No.3,796,669; a process of using isocyanate wall materials as described inU.S. Pat. No. 3,914,511; a process of using urea-formaldehyde orurea-formaldehyde-resorcinol wall-forming materials as described in U.S.Pat. Nos. 4,001,140, 4,087,376 and 4,089,802; a process of usingmelamine-formaldehyde resins hydroxypropyl cellulose or otherwall-forming materials as described in U.S. Pat. No. 4,025,455; an insitu process utilizing polymerization of monomers as described in U.K.Patent No. 867,797 and U.S. Pat. No. 4,001,140; an electrolyticdispersion and cooling process as described in U.K. Pat. Nos. 952,807and 965,074; a spray-drying process as described in U.S. Pat. No.3,111,407 and U.K. Pat. No. 930,422; etc. It is preferable, though notlimitative, that the microcapsule is prepared by emulsifying a corematerial containing the polymerizable compound and forming a polymericmembrane (i.e., shell) over the core materials.

When the emulsion of the polymerizable compound (including thedispersion of the microcapsule) has been prepared by using thelight-sensitive composition, the emulsion can be used as the coatingsolution of the light-sensitive material. The coating solution can bealso prepared by mixing the emulsion of the polymerizable compound andthe silver halide emulsion.

A light-sensitive material of the invention can be prepared by coatingand drying the above-prepared coating solution on a support in theconventional manner.

Use of the light-sensitive material is described below.

In the use of the light-sensitive material of the invention, adevelopment process is conducted simultaneously with or after imagewiseexposure.

Various exposure means can be employed in the image-wise exposure, andin general, the latent image of the silver halide is obtained byimagewise exposure to radiation including visible light. The type oflight source and exposure conditions can be selected depending on thelight-sensitive wavelengths determined by spectral sensitization orsensitivity of silver halide. The original image can be eithermonochromatic image or color image.

Development of the light-sensitive material can be conductedsimultaneously with or after the imagewise exposure. The development canbe conducted using a developing solution in the same manner as the imageforming method described in Japanese Patent Publication No.45(1970)-11149. The image forming method described in Japanese PatentProvisional Publication No. 61(1986)-69062 which employs a heatdevelopment process has an advantage of simple procedures and shortprocessing time because of the dry process. Thus, the latter method ispreferred as the development process of the light-sensitive material.

Heating in the heat development process can be conducted in variousknown manners. The heating layer which is arranged on thelight-sensitive material can be used as the heating means. The heatingtemperature for the development process usually ranges from 80° C. to200° C., and preferably from 100° C. to 160° C. Various heating patternsare applicable. The heating time is usually from 1 second to 5 minutes,and preferably from 5 seconds to 1 minute.

During the above development process, a polymerizable compound in aportion where a latent image of the silver halide has been formed or ina portion where a latent image of the silver halide has not been formedis polymerized. In a general system, the polymerizable compound in aportion where the latent image has been formed is polymerized. If anature or amount of the reducing agent is controlled, the polymerizablecompound in a portion where the latent image has not been formed can bepolymerized in the same manner as the light-sensitive material describedin Japanese Patent Provisional Publication No. 61(1986)-260241.

In the above development process, a polymer image can be formed on thelight-sensitive layer. A pigment image can be also obtained by fixingpigments onto the polymer image.

The image can be also formed on the image-receiving material. Theimage-receiving material is described hereinbelow. The image formingmethod employing the image-receiving material or the image-receivinglayer is described in Japanese Patent Provisional Publication No.61(1986)-278849.

Examples of the material employable as the support of theimage-receiving material include baryta paper in addition to variousexamples which can be employed as the support of the knownlight-sensitive material.

The image-receiving material is usually prepared by providing theimage-receiving layer on the support. The image-receiving layer can beconstructed according to the color formation system. In the case that apolymer image is formed on the image-receiving material and that a dyeor pigment is employed as the color image forming substance, theimage-receiving material be composed of a simple support.

For example, when a color formation system using a color former anddeveloper is employed, the developer can be contained in theimage-receiving layer. Further, the image-receiving layer can becomposed of at least one layer containing a mordant. The mordant can beselected from the compounds known in the art of the conventionalphotography according to the kind of the color image forming substance.If desired, the image-receiving layer can be composed of two or morelayers containing two or more mordants different in the mordanting powerfrom each other.

The image-receiving layer preferably contains a polymer as binder. Thebinder which may be employed in the above-mentioned light-sensitivelayer is also employable in the image-receiving layer.

The image-receiving layer can be composed of two or more layersaccording to the above-mentioned functions. The thickness of theimage-receiving layer preferably ranges from 1 to 100 μm, morepreferably from 1 to 20 μm.

After the development process, by pressing the light-sensitive materialon the image-receiving material to transfer the unpolymerizedpolymerizable compound to the image-receiving material, a polymer imagecan be obtained in the image-receiving material. The process forpressing can be carried out in various known manners.

In the case that the light-sensitive layer contains a color imageforming substance, the color image forming substance is fixed bypolymerization of the polymerizable compound. Then, by pressing thelight-sensitive material in contact with the image-receiving material totransfer the color image forming substance in unfixed portion, a colorimage can be produced on the image-receiving material.

The light-sensitive material can be used for monochromatic or colorphotography, printing, radiography, diagnosis (e.g., CRT photography ofdiagnostic device using supersonic wave), copy (e.g., computer-graphichard copy), etc.

The present invention is further described by the following exampleswithout limiting the invention.

COMPARISON EXAMPLE 1 Preparation of silver halide emulsion

In 1,000 ml of water were dissolved 20 g of gelatin and 1 g of potassiumbromide, and the resulting gelatin solution was kept at 70° C. To thegelatin solution, 600 ml of an aqueous solution containing 70 g ofpotassium bromide and 600 ml of an aqueous solution containing 0.59 moleof silver nitrate were added simultaneously at the same feed rate over aperiod of 20 minutes. Further, after 5 mimutes, to the resulting mixture100 ml of an aqueous solution containing 1.7 g of potassium iodide and100 ml of an aqueous solution containing 0.01 mole of silver nitratewere added simultaneously at the same feed rate over a period of 3minutes to obtain a silver iodobromide emulsion having uneven grain sizedistribution and an average grain size of 0.18 μm. The coefficient ofvariation of the grain size distribution of the silver halide grains was32%.

The emulsion was washed for desalting and then subjected to chemicalsensitization with 5 mg of sodium thiosulfate and 20 mg of4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene at 60° C. to obtain thesilver halide emulsion (a). The yield of the emulsion was 600 g.

Preparation of silver benzotriazole emulsion

In 3,000 ml of water were dissolved 28 g of gelatin and 13.2 g ofbenzotriazole, and the solution was kept at 40° C. while stirring. Tothe solution was added 100 ml of an aqueous solution of 17 g of silvernitrate over 2 min. An excessive salt were sedimented by pH-adjustmentand removed from the resulting emulsion. Thereafter, the emulsion wasadjusted to pH 6.30 to obtain a silver benzotriazole emulsion. The yieldof the emulsion was 400 g.

Preparation of light-sensitive composition

In 100 g of trimethylolpropane triacrylate were dissolved 0.2 g of thefollowing copolymer, 10 g of Pargascript Red I-6-B (tradename ofLilia-Geigy) and 2 g of Emulex NP-8 (tradename, preduced by NipponEmulsion Co., Ltd.). ##STR1##

To 18 g of the resulting solution was added to a solution in which 0.2 gof the following reducing agent (I) and 0.6 g of the following reducingagent (II) were dissolved in 1.8 g of methylene chloride. ##STR2##

Further, to the resulting solution were added 2 g of the silver halideemulsion (a) and 2 g of the silver benzotriazole emulsion, and themixture was stirred at 15,000 r.p.m. for 5 min. to obtain alight-sensitive composition.

Preparation of light-sensitive microcapsule

To the light-sensitive composition was dissolved 10 g of an adduct ofxylylene diisocyanate and trimethylolpropane, (tradename "TakenateD110N" produced by Takeda Chemical Industries, Ltd.). The resultingsolution was added to 70 g of 4% aqueous solution of methyl cellulose,and the mixture was stirred at 7,000 r.p.m. for 2 minutes to obtain anemulsion. The emulsion was subjected to reaction for 2 hours at 40° C.while stirring at 1,000 r.p.m. to obtain a dispersion containinglight-sensitive microcapsules which have a shell material made ofpolyurea resin.

Preparation of light-sensitive material

To 10.0 g of the light-sensitive microcapsule dispersion were added 1.0g of 10% aqueous solution of Emulex NP-8 (tradename, produced by NipponEmulsion, Co., Ltd.) and 5 g of 5% aqueous solution of guanidinetrichroloacetate to prepare a coating solution. The coating solution wasuniformly coated on a cast-coat paper having a basis weight of 85 gusing a coating rod to a wet thickness of 70 μm and dried at about 30°C. to obtain a light-sensitive material (A).

EXAMPLE 1 Preparation of silver halide emulsion

The silver emulsion (b) was prepared in the same manner as in ComparisonExample 1, except that the gelatin solution was kept at 60° C. in placeof 70° C., and to the gelatin solution, 600 ml of an aqueous solutioncontaining 70 g of potassium bromide and 600 ml of an aqueous solutioncontaining 0.59 mole of silver nitrate were added over a period of 40minutes in place of 20 minutes.

Further, each of the silver halide emulsions (c) and (d) was prepared inthe same manner except that the stirring rate and the mixing time werevarried.

The coefficient of variation in the grain size distribution and thecrystal habit of the silver halide grains in the above silver halideemulsions are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                        Silver   Average    Coefficient                                                                             Crystal                                         Halide   Grain      of        Habit of                                        Emulsion Size       Variation Grain                                           ______________________________________                                        (a)      0.18 μm 32 %      tetradecahedral                                 (b)      0.18 μm 18 %      tetradecahedral                                 (c)      0.18 μm 14 %      tetradecahedral                                 (d)      0.18 μm  9 %      tetradecahedral                                 ______________________________________                                    

Preparation of light-sensitive material

The light-sensitive materials (B) to (D) were prepared in the samemanner as in Comparison Example 1, except that the above silver halideemulsions (b) to (d) were used, respetively, in place of the silverhalide emulsion (a).

Preparation of image-receiving material

To 125 g of water was added 11 g of 40% aqueous solution of sodiumhexametaphosphate, and were further added 34 g of zinc3,5-di-α-methylbenzylsalicylate and 82 g of 55% slurry of calciumcarbonate, followed by coarsely dispersing in a mixer. The coarsedispersion was then finely dispersed in Dynomile dispersing device. To200 g of the resulting dispersion were added 6 g of 50% latex of SBR(styrene-butadiene rubber) and 55 g of 8% aqueous solution of polyvinylalcohol, and the resulting mixture was made homogenous.

The mixture was then uniformly coated on an art paper having basisweight of 43 g/m² to give a layer having a wet thickness of 30 μm anddried to obtain an image-receiving material.

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Comparison Example 1and Example 1 was imagewise exposed to light through a filter (wedge) inwhich the density continuously changed, using a tungsten lamp at 2,000lux for 1 second and then heated on a hot plate at 125° C. for 10 to 50seconds. Each of the exposed and heated light-sensitive materials wasthen combined with the image-receiving material and passed through pressrolls under pressure of 350 kg/cm² to obtain a magenta positive image onthe image receiving material. The density of the obtained image wasmeasured using Macbeth reflection densitometer.

The results are set forth in Table 2. In Table 2, "Contrast in Image"means the obtained maximum contrast value ("maximum density" - "minimumdensity") concerning each of the light-sensitive material, and "HeatingTime" means the time required to obtain the above maximum contrast.

                  TABLE 2                                                         ______________________________________                                        Light-   Silver       Contrast                                                Sensitive                                                                              Halide       in       Heating                                        Material Emulsion     Image    Tome                                           ______________________________________                                        (A)      (a)          0.72     14 seconds                                     (B)      (b)          0.96     12 seconds                                     (C)      (c)          1.01     10 seconds                                     (D)      (d)          1.04     10 seconds                                     ______________________________________                                    

It is apparent from the results in Table 2 that each of thelight-sensitive materials (B), (C) and (D) forms a clear positive imagewhich has a high maximum density and a low minimum density. It is alsoapparent that the clear image was obtained in the short-timedevelopment.

COMPARISON EXAMPLE 2 Preparation of silver halide emulsion

The silver halide emulsion (a') was prepared in the same manner as inComparison Example 1, except that the emulsion was not subjected tochemical sensitization with 5 mg of sodium thiosulfate and 20 mg of4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene.

Preparation of light-sensitive material

The light-sensitive material (E) was prepared in the same manner as inComparison Example 1, except that the above silver halide emulsion (a')was used in place of the silver halide emulsion (a).

EXAMPLE 2 Preparation of silver halide emulsion

Each of the silver halide emulsions (b') to (d') was prepared in thesame manner as in Example 1, except that each of the emulsions was notsubjected to chemical sensitization with 5 mg of sodium thiosulfate and20 mg of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene.

Preparation of light-sensitive material

Each of the light-sensitive materials (F) to (H) was prepared in thesame manner as in Example 1, except that each of the above silver halideemulsions (b') to (d') was respectively used in place of each of thesilver halide emulsions (b) to (d).

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Comparison Example 2and Example 2 was evaluated in the same manner as in Comparison Example1 and Example 1. The density of each of the obtained image on theimage-receiving material was measured using Macbeth reflectiondensitometer.

The results are set forth in Table 3. In Table 3, "Contrast in Image"and "Heating Time" have the same meanings in Table 2.

                  TABLE 3                                                         ______________________________________                                        Light-   Silver       Contrast                                                Sensitive                                                                              Halide       in       Heating                                        Material Emulsion     Image    Time                                           ______________________________________                                        (E)      (a')         0.86     14 seconds                                     (F)      (b')         0.99     13 seconds                                     (G)      (c')         1.08     11 seconds                                     (H)      (d')         1.07     11 seconds                                     ______________________________________                                    

It is apparent from the results in Table 3 that in a system employing nochemical sensitization, the light-sensitive material of the inventiongives a clear image in the short-time development.

COMPARISON EXAMPLE 3 Preparation of light-sensitive material

The light-sensitive material (I) was prepared in the same manner as inComparison Example 2, except that the silver benzotriazole emulsion wasnot used.

EXAMPLE 3 Preparation of light-sensitive material

Each of the light-sensitive materials (J) to (L) was prepared in thesame manner as in Example 2, except that the silver benzotriazoleemulsion was not used.

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Comparison Example 3and Example 3 was evaluated in the same manner as in Comparison Example1 and Example 1. The density of each of the obtained image on theimage-receiving material was measured using Macbeth reflectiondensitometer.

The results are set forth in Table 4. In Table 4, "Contrast in Image"and "Heating Time" have the same meanings in Table 2.

                  TABLE 4                                                         ______________________________________                                        Light-   Silver       Contrast                                                Sensitive                                                                              Halide       in       Heating                                        Material Emulsion     Image    Time                                           ______________________________________                                        (J)      (a')         0.88     20 seconds                                     (K)      (b')         1.02     18 seconds                                     (L)      (c')         1.0      17 seconds                                     (M)      (d')         1.10     15 seconds                                     ______________________________________                                    

It is apparent from the results in Table 4 that in a system employing noorganic silver salt (silver benzotriazole), the light-sensitive materialof the invention gives a clear image in the short-time development.

COMPARISON EXAMPLE 4 Preparation of light-sensitive material

The light-sensitive material (M) was prepared in the same manner as inComparison Example 3, except that 1 g of the silver halide emulsion (a')was used in place of 2 g of the silver halide emulsion (a').

EXAMPLE 4 Preparation of light-sensitive material

Each of the light-sensitive materials (N) to (P) was prepared in thesame manner as in Example 3, except that 1 g of each of the silverhalide emulsion (b') to (d') was respectively used in place of 2 g ofeach of the silver halide emulsion (b') to (d').

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Comparison Example 4and Example 4 was evaluated in the same manner as in Comparison Example1 and Example 1. The density of each of the obtained image on theimage-receiving material was measured using Macbeth reflectiondensitometer.

The results are set forth in Table 5. In Table 5, "Contrast in Image"and "Heating Time" have the same meanings in Table 2.

                  TABLE 5                                                         ______________________________________                                        Light-   Silver       Contrast                                                Sensitive                                                                              Halide       in       Heating                                        Material Emulsion     Image    Time                                           ______________________________________                                        (M)      (a')         0.43     23 seconds                                     (N)      (b')         0.81     19 seconds                                     (O)      (c')         0.89     18 seconds                                     (P)      (d')         0.98     16 seconds                                     ______________________________________                                    

It is apparent from the results in Table 5 that even if the amount ofthe silver halide emulsion is small, the light-sensitive material of theinvention gives a clear image in the short-time development.

I claim:
 1. A light-sensitive material comprising a support and alight-sensitive layer containing silver halide grains, a reducing agent,an ethylenically unsaturated polymerizable compound, wherein the silverhalide grains and polymerizable compound are contained in microcapsuleswhich are dispersed in the light-sensitive layer, said silver halidegrains having such a grain size distribution that the coefficient orvariation in terms of σ/r is not more than 20%, wherein σ means astandard deviation of the grain size and r means an average grain size,and said polymerizable compound being contained in microcapsules in anamount of 5 to 1.2×10⁵ times by weight as much as the amount of thesilver halide grains.
 2. The light-sensitive material as claimed inclaim 1, wherein the coefficient of variation of the silver halidegrains is not more than 15%.
 3. The light-sensitive material as claimedin claim 1, wherein the average grain size of the silver halide grainsis in the range of from 0.001 to 5 μm.
 4. The light-sensitive materialas claimed in claim 1, wherein the total silver content in thelight-sensitive layer is in the range of from 0.1 mg/m² to 10 g/m². 5.The light-sensitive material as claimed in claim 1, wherein thelight-sensitive layer further contains a color image forming substance.6. The light-sensitive material as claimed in claim 1, wherein theaverage grain size of the silver halide is not more than one-fifth ofthe average size of the microcapsules.
 7. An image-forming method whichcomprises:imagewise exposing a light-sensitive material comprising asupport and a light-sensitive layer containing silver halide grains, areducing agent, an ethylenically unsaturated polymerizable compound,wherein the silver halide grains and polymerizable compound arecontained in microcapsules which are dispersed in the light-sensitivelayer, said silver halide grains having such a grain size distributionthat the coefficient or variation in terms of σ/r is not more than 20%,wherein σ means a standard deviation of the grain size and r means anaverage grain size, and said polymerizable compound being contained inmicrocapsules in an amount of 5 to 1.2×10⁵ times by weight as much asthe amount of the silver halide grains, to form a latent image of thesilver halide; and simultaneously or thereafter heating thelight-sensitive material to polymerize the polymerizable compound withinthe area where the latent image of the silver halide has been formed. 8.The image-forming method as claimed in claim 7, wherein after heatingthe light-sensitive material, the light-sensitive material is pressed onan image-receiving material to transfer the obtained image to theimage-receiving material.
 9. The image-forming method as claimed inclaim 7, wherein the total silver content in the light-sensitive layerof the light-sensitive material is in the range of from 0.1 mg/m² to 10g/m².
 10. An image-forming method which comprises:imagewise exposing alight-sensitive material comprising a support and a light-sensitivelayer containing silver halide grains, a reducing agent, anethylenically unsaturated polymerziable compound, wherein the silverhalide grains and polymerizable compound are contained in microcapsuleswhich are dispersed in the light-sensitive layer, said silver halidegrains having such a grain size distribution that the coefficient orvariation in terms of σ/r is not more than 20%, wherein σ means astandard deviation of the grain size and r means an average grain size,and said polymerizable compound being contained in microcapsules in anamount of 5 to 1.2×10⁵ times by weight as much as the amount of thesilver halide grains, to form a latent image of the silver halide; andsimultaneously or thereafter heating the light-sensitive material topolymerize the polymerizable compound within the area where the latentimage of the silver halide has not been formed.
 11. The image-formingmethod as claimed in claim 10, wherein after heating the light-sensitivematerial, the light-sensitive material is pressed on an image-receivingmaterial to transfer the obtained image to the image-receiving material.12. The image-forming method as claimed in claim 10, wherein the totalsilver content in the light-sensitive layer of the light-sensitivematerial is in the range of from 0.1 mg/m² to 10 g/m².
 13. Thelight-sensitive material as claimed in claim 1, wherein the silverhalide grains are arranged in a shell of the microcapsule, and thepolymerizable compound is arranged in a core of the microcapsule. 14.The light-sensitive material as claimed in claim 1, wherein the reducingagent is contained in the microcapsules.